diff --git a/sys/compat/ndis/subr_ndis.c b/sys/compat/ndis/subr_ndis.c
index e1ba8cc12cd..914c85887e4 100644
--- a/sys/compat/ndis/subr_ndis.c
+++ b/sys/compat/ndis/subr_ndis.c
@@ -1287,7 +1287,7 @@ NdisMRegisterIoPortRange(offset, adapter, port, numports)
 	if (rman_get_size(sc->ndis_res_io) < numports)
 		return (NDIS_STATUS_INVALID_LENGTH);
 
-	*offset = (void *)rman_get_start(sc->ndis_res_io);
+	*offset = (void *)(uintptr_t)rman_get_start(sc->ndis_res_io);
 
 	return (NDIS_STATUS_SUCCESS);
 }